31. Based on an order-of-magnitude estimate, what is the radius of the Earth in the unit of kilometer (km)? Hint: The meter was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole along a great circle.
(A) 2
(B) 4
(C) 6
(D) 8
(E) 10

27. CdS can be described as cubic closest packed anions with the cations in tetrahedral holes. What fraction of the tetrahedral holes is occupied by the cations? (A) 0.125 (B) 0.25 (C) 0.50 (D) 0.75 (E) 1.0

28. For the reaction 3A(g) + 2B(g) → 2C(g) + 2D(g), the following data was collected at constant temperature. Determine the correct rate law for this reaction.  (A) Rate = k[A][B] (B) Rate = k[A][B]2 (C) Rate = k[A]3 [B]2 (D)(E) Rate = k[A]2 [B]

29. What is the number of the half-lives required for a radioactive element to decay to about 6% of its original activity? (please choose the nearest number) (A) 2 (B) 3 (C) 4 (D) 5 (E) 6

30. Identify the element of Period 2 which has the following successive ionization energies, in kJ/mol.   (A) Li (B) B (C) O (D) Ne (E) None of these

32. A part of the square that has sides of length L is removed from one corner. The center of mass of the remainder moves from C to C'. The displacement of the x coordinate of the center of mass (from C to C') is ______. (A) (2/3)L (B) (1/6)L (C) (1/8)L (D) (1/10)L (E) (1/12)L

複選題33. The string and the pulley are massless, and the coefficient of static and kinetic frictions are 0.2 and 0.1, respectively, for both table 1 (T1) and 2 (T2). If m1 = 2 kg, m2 = 3 kg, and m = 1.5 kg, find the acceleration of m. (Gravitational acceleration g = 10 m/s2 )  (AB) 7.7 m2 /s (AC) 8.7 m2 /s (AD) 9.7 m2 /s (AE) 10.7 m2 /s (BC) 11.7 m2 /s (BD)一律送分

34. Aluminum Rod #1 has a length L and a diameter d. Aluminum Rod #2 has a length 2L and a diameter 2d. If Rod #1 is under tension T and Rod #2 is under tension 2T, how do the changes in length of the two rods compare? (A) They are the same. (B) Rod #1 has double the change in length that Rod #2 has. (C) Rod #2 has double the change in length that Rod #1 has. (D) Rod #1 has quadruple the change in length that Rod #2 has. (E) Rod #2 has quadruple the change in length that Rod #1 has.

35. A toy car is running on a banked circular track of radius 10 m, as shown below. If the car weighs 5 kg and on wet ice, find the maximum velocity for the car to keep on the track without skid. (Gravitational acceleration g = 10 m/s2 , cos30° = 0.87, cos60° = 0.5)  (A) 5.4 m/s (B) 7.6 m/s (C) 9.4 m/s (D) 12.6 m/s (E) 15.7 m/s

36. A small block of mass m rests on the sloping side of a triangular block of mass M which itself rests on a horizontal table as shown in the figure below. Assuming all surfaces are frictionless, determine the magnitude of the force F that must be applied to M so that m remains in a fixed position relative to M. Hint: 1. Take x and y axes horizontal and vertical. 2. Focus at the object m. (A) mg sinθ (B) mg tanθ (C) (m+M)g tanθ(D) (m+M)g sinθ(E) None of these

37. The four tires of an automobile are inflated to a gauge pressure of 2.0 × 105 N/m2 (29 psi). Each of the four tires has an area of 0.024 m2 that is in contact with the ground. Determine the weight of the auto. (A) 4.80 × 103N (B) 1.92 × 104N (C) 7.68 × 104N (D) 8.33 × 106N (E) 2.08 × 107N